1. Field of the Invention
This invention relates to a pellicle placed on a mask employed in a photolitho process corresponding to a part of processes for manufacturing a semiconductor integrated circuit, a system for identifying the pellicle, and a method of identifying the pellicle.
2. Description of the Related Art
In general, a mask is a semiconductor circuit pattern plate used when semiconductor patterns are transferred onto a wafer substrate.
This type of mask is one in which semiconductor circuit patterns are formed over a substrate such as quartz by a thin-film metal such as Cr or the like. There may be cases where a pellicle is placed on the mask to protect the surface of the mask from foreign particles such as dust or the like.
Upon control of the mask, information about the name (or figure number) a semiconductor manufactured by the mask, the name of its owner, a calendar, etc. are provided on the surface of the mask except for the semiconductor circuit patterns.
In recent years, there may be cases in which a figure number on a mask is displayed in the form of bar codes. When the mask is set to an exposure device in this case, the device automatically reads the figure number based on the bar codes to thereby lessen the load on a worker and prevent the worker from misreading the figure number.
In regard to the pellicle placed on the mask, a pellicle figure number is engraved or marked on the side of a pellicle frame. The pellicle drawing or figure number is determined according to the type of exposure device to be used and an exposure wavelength employed in the exposure device. The worker identifies the pellicle and uses it according to the figure number.
However, there may be cases in which when marks or the like capable of being handled with a plurality of exposure devices are placed within the mask in advance and the corresponding exposure devices used upon device development and device mass-production are selected, the present pellicles in use are renewed or changed to pellicles having different pellicle frame shapes according to the selected exposure devices and they are used. There may be cases in which even in the case of the same pellicle frame shapes, pellicle membrane placed on their pellicle frames are different in material from each other according to the exposure wavelength used in each exposure device.
In many cases, a pellicle membrane for G- and I-line wavelengths uses nitrocellulose as a raw material. A pericle film for a KrF excimer-ray""s wavelength makes use of fluoropolymer as a material. The pellicle membrane for the KrF excimer-ray""s wavelength has transmissivity sufficient for the G- and I-line wavelengths and also has resistance thereto. Conversely, the pellicle memmbrane for the G- and I-line wavelengths has transmissivity insufficient for the KrF excimer-ray""s wavelength and resistance thereto insufficient therefor. When the KrF excimer-ray""s wavelength is allowed to pass through the pellicle membrane for the G- and I-line wavelengths erroneously, the mask itself might be damaged as a result of impairment of the pellicle membrane.
It is thus necessary to select the proper pellicle before the pellicle is placed over the mask and confirm the pellicle on the mask before the exposure thereof by the exposure device. Particularly when the type of pellicle is renewed, an ID such as a bar code or the like formed on the mask in advance upon mask fabrication cannot cope with it.
With the foregoing in view, it is therefore an object of the present invention to provide a pellicle, an identification system thereof and a method of identifying the pellicle, which permit each individual identification with accuracy and ease.
According to one aspect of the invention, for achieving the above object, there is provided a pellicle, comprising: a pellicle membrane; a pellicle frame for sticking the pellicle membrane; a sticking portion provided on a surface of the pellicle frame , which is located on the side opposite to a sticking surface of the pellicle membrane; and a portion for identifying the pellicle, which comprises a conductive film and predetermined patterns composed of conductors formed on the conductive film.
According to another aspect of the invention, there is provided a pellicle identifying system, comprising: a pellicle including, a pellicle membrane; a pellicle frame for sticking the pellicle membrane; a sticking portion provided on a surface of the pellicle frame, which is located on the side opposite to a sticking surface of the pellicle membrane; and a portion for identifying the pellicle, which comprises a conductive film and predetermined patterns composed of conductors formed on the conductive film; signal lines electrically connected to the predetermined patterns respectively; and a reader for reading a signal from each signal line.
According to a further aspect of the invention, there is provided a pellicle identifying method, comprising the following steps of: fixing onto a mask, a pellicle including a pellicle membrane, a pellicle frame for sticking the pellicle membrane, a sticking portion provided on a surface of the pellicle frame, which is located on the side opposite to a sticking surface of the pellicle membrane, and a portion for identifying the pellicle, which comprises a conductive film and predetermined patterns composed of conductors formed on the conductive film; connecting the predetermined patterns to one ends of signal lines formed on the mask respectively; connecting a reader to the other ends of the signal lines; and supplying a source potential to the conductive film to read a signal from each of the signal lines connected to the predetermined patterns by the reader.
Typical ones of various inventions of the present application have been shown in brief. However, the various inventions of the present application and specific configurations of these inventions will be understood from the following description.